This invention relates to a decontamination device for removing metalliferous particles from a mixture. In particular, it relates to a decontamination device for removing metalliferous particles from soap-based lubricating powder used in the process of wire extrusion. It should be appreciated however that the present invention is a decontamination device which could be used to remove metalliferous particles from mixtures with many dry fine-grained substances.
It is increasingly recognised within industry and by the population at large that the disposal of industrial waste products requires a more sophisticated approach. Mere dumping of same, for example in landfills, is simply no longer acceptable in light of current concern for protecting the environment. Quite apart from environmental ramifications, it is also economically desirable to reduce industrial waste as far as practicable.
Often the base component of a contaminated substance has continuing integrity for further industrial application, save that it is contaminated. Where decontamination methods are expensive and time consuming, the substance is simply dumped as waste rather than efforts being made to recycle or re-use the substance.
Wire drawing procedures exhibit significant wastage of lubricant powder. Approximately 90% of all powder used becomes too contaminated for use and is dumped in landfills according to industry sources. The powder becomes contaminated with fine metal particles which ultimately destroy the lubricating capabilities of the powder. Generally, the lubricant powder has a particle size ranging from less than one micron to approximately two millimeters in diameter. The metal particles contaminating the powder comprise either fine slivers and, to a greater extent, fine grain particles of approximately one micron in diameter.
Preliminary investigations suggest that at least some 50 tonnes of contaminated soap based powder lubricant is dumped in landfills in New Zealand alone. Clearly internationally the dumping of contaminated lubricant powder forms a serious environmental problem.
It would be desirable to provide a financially viable and convenient method of removing metal contaminants from mixtures with substances such as lubricant powders to permit re-use of such powders, or any other mixture experiencing contamination by metalliferous particles.
Grate magnets have been used in the past to separate ferrous components from powders. These devices comprise a single magnet or a row of magnets and material is fed through the grate in a single pass operation. Metallic material not attracted to the grate escapes the process.
A number of decontamination devices have been patented in the past. As an example U.S. Pat. No. 4,370,228 discloses a device having an oil storage tank for storing used cutting oil. Magnetic particles contained in the cutting oil are removed by a magnetic conveyor device which is immersed in the oil and particles attracted to the conveyor are continuously removed at a dry zone. The device described in U.S. Pat. No. 4,370,228 is typical of devices in which particulate material is removed from a liquid. It is considered that there are many instances where such methods are not necessary or desirable. New Zealand Patent Nos. 140744 and 116764 describe magnetic separators where xe2x80x9cdryxe2x80x9d powders contaminated by metal particles are forced to pass rotating or circulating magnets. However, in both instances the efficiency of the separation process appears to be entirely dependent upon the strength of the magnets to a separate metallic particles from powder particles.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful alternative.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.
According to one aspect of the invention there is provided a device for removing metalliferous particles from a mixture including:
(a) a chamber,
(b) means for delivering the powder mixture to the chamber in a fluid stream,
(c) a magnet retained within the chamber in proximity to the fluid stream,
(d) means for the removal of metalliferous particles attracted to the magnet.
The device can include means for promoting movement of the mixture in a counter direction to the fluid stream.
Said means for promoting movement of the mixture is an airstream which promotes secondary delivery to the magnet of the metalliferous particles not attaching to the magnet from the fluid stream.
The device can include means for separate collection of contaminated and clean particulate material from the powder mixture.
The means for promoting movement of the mixture counter to the fluid stream can be a ducted airflow promoted by a fan.
The airflow can be directed at an acute angle to the fluid stream.
The contaminated mixture can be stored in a container and the material is dispersed to a position adjacent a first face of the magnet.
The device can include a scraping device which continuously wipes the first surface of the magnet.
The device can include a front wall opposite to the first face of the magnet which defines one side of a passage into which the fluid stream is directed.
The dispersal of the mixture into the fluid stream can be metered by a metering device.
The metering device can include an auger.
The scraper can rotate in a direction sympathetic to the fluid stream.
According to a further aspect of the present invention there is provided a method of removing metalliferous particles from a mixture comprising directing contaminated material to a fluid stream within a chamber positioning a magnetic device adjacent an outlet from the fluid stream to attract metalliferous particles thereto.
The method can include means for separate collection of contaminated and clean material from the mixture.
The method can include means for promoting movement of the mixture counter to the fluid stream.
The airflow is directed at an acute angle with respect to the fluid stream.
According to a further aspect of the present invention there is provided a method of removing metalliferous particles from a mixture comprising directing the mixture in a fluid stream at a magnetic surface from a feeding device and providing a controlled turbulent airflow in a direction countering the fluid stream.